Capo is a Mac-only program that lets you learn to play songs in your music library via spectrum analysis, automatic chord recognition, and more. I have absolutely no use for this right now, but this is WAY cool.
TUAW has a very useful reference post on how to unfreeze your Mac via the Terminal, including SSHing in from another machine. Most useful to me — the right commands to remotely logout a GUI user via a SSH session.
I’ve been trying to figure out how to download old podcasts of This American Life — stupid iTunes keeps turning my subscription off if I haven’t listened to an episode in a while. Luckily, someone else shared the URL format for the files:
http://audio.thisamericanlife.org/jomamashouse/ismymamashouse/EPISODENUMBER.mp3
Episode numbers do not have any leading zeros. 
And don’t forget to donate to TAL.
This Lifehacker article on using Kelly Blue Book online via a cellphone saved someone money has links to other helpful car-buying tips. Worth a read.
iPodMeister gives you an iPad (or iPhone, iPod Touch, or hard drive) for your old CDs and DVDs. They’ll even rip the music to MP3 for you. Interesting. Hat-tip: TUAW.
There’s a pretty hardcore mod you can use to add eSata support to your AppleTV. This completely replaces the internal hard drive, and is NOT for the faint of heart!
The Apple Blog explains how to expand Wake On Demand support under OS X 10.6. Sounds useful.
rEFIt is a boot menu for EFI-based Intel Macs. Might be interesting.
Here’s a thread on Webmaster World with some interesting changes to the .htaccess rules that ship with WordPress that supposedly really speed up site loading times. Might be worth checking out; I wonder if a WP Trac ticket exists for this?
Here’s a very detailed guide and install scripts on installing from a full retail OS X 10.5.8 DVD on a Gigabyte GA-EX58-UD5 Core i7 motherboard. Hackintosh, anyone?